Earth-boring tools having pockets for receiving cutting elements therein and methods of forming such pockets and earth-boring tools

ABSTRACT

Methods of forming cutting element pockets in earth-boring tools include machining at least one recess to define at least one surface of a cutting element pocket using a cutter oriented at an angle to a longitudinal axis of the cutting element pocket. Methods of forming earth-boring tools include forming a bit body and forming at least one cutting element pocket therein using a rotating cutter oriented at an angle relative to a longitudinal axis of the cutting element pocket being formed. Earth-boring tools have a bit body comprising a first surface defining a lateral sidewall of a cutting element pocket, a second surface defining an end wall of the cutting element pocket, and another surface defining a groove located between the first and second surfaces that extends into the body to enable a cutting element to abut against an area of the lateral sidewall and end wall of the pocket.

FIELD OF THE INVENTION

The present invention relates generally to earth-boring tools andmethods of forming earth-boring tools. More particularly, the presentinvention relates to methods of securing cutting elements toearth-boring tools and to tools formed using such methods.

BACKGROUND OF THE INVENTION

Rotary drill bits are commonly used for drilling bore holes or wells inearth formations. One type of rotary drill bit is the fixed-cutter bit(often referred to as a “drag” bit), which typically includes aplurality of cutting elements secured to a face region of a bit body.Generally, the cutting elements of a fixed-cutter type drill bit haveeither a disk shape or, in some instances, a more elongated,substantially cylindrical shape. A cutting surface comprising a hard,super-abrasive material, such as mutually bound particles ofpolycrystalline diamond forming a so-called “diamond table,” may beprovided on a substantially circular end surface of a substrate of eachcutting element. Such cutting elements are often referred to as“polycrystalline diamond compact” (PDC) cutting elements or cutters.Typically, the PDC cutting elements are fabricated separately from thebit body and secured within pockets formed in the outer surface of thebit body. A bonding material such as an adhesive or, more typically, abraze alloy may be used to secured the cutting elements to the bit body.

The bit body of a rotary drill bit typically is secured to a hardenedsteel shank having an American Petroleum Institute (API) threadconnection for attaching the drill bit to a drill string. The drillstring includes tubular pipe and equipment segments coupled end to endbetween the drill bit and other drilling equipment at the surface.Equipment such as a rotary table or top drive may be used for rotatingthe drill string and the drill bit within the bore hole. Alternatively,the shank of the drill bit may be coupled directly to the drive shaft ofa down-hole motor, which then may be used to rotate the drill bit.

Referring to FIG. 1, a conventional fixed-cutter earth-boring rotarydrill bit 10 includes a bit body 12 that has generallyradially-projecting and longitudinally-extending wings or blades 14,which are separated by junk slots 16 extending from channels on the face20 of the bit body 12. A plurality of PDC cutting elements 18 areprovided on the blades 14 extending over face 20 of the bit body 12. Theface 20 of the bit body 12 includes the surfaces of the blades 14 thatare configured to engage the formation being drilled, as well as theexterior surfaces of the bit body 12 within the channels and junk slots16. The plurality of PDC cutting elements 18 may be provided along eachof the blades 14 within cutting element pockets 22 formed inrotationally leading edges thereof, and the PDC cutting elements 18 maybe supported from behind by buttresses 24, which may be integrallyformed with the bit body 12.

The drill bit 10 may further include an API threaded connection portion30 for attaching the drill bit 10 to a drill string (not shown).Furthermore, a longitudinal bore (not shown) extends longitudinallythrough at least a portion of the bit body 12, and internal fluidpassageways (not shown) provide fluid communication between thelongitudinal bore and nozzles 32 provided at the face 20 of the bit body12 and opening onto the channels leading to junk slots 16.

During drilling operations, the drill bit 10 is positioned at the bottomof a well bore hole and rotated while drilling fluid is pumped throughthe longitudinal bore, the internal fluid passageways, and the nozzles32 to the face 20 of the bit body 12. As the drill bit 10 is rotated,the PDC cutting elements 18 scrape across and shear away the underlyingearth formation. The formation cuttings mix with and are suspendedwithin the drilling fluid and pass through the junk slots 16 and upthrough an annular space between the wall of the bore hole and the outersurface of the drill string to the surface of the earth formation.

The bit body 12 of a fixed-cutter rotary drill bit 10 may be formed fromsteel. Such steel bit bodies are typically fabricated by machining asteel blank (using conventional machining processes including, forexample, turning, milling, and drilling) to form the blades 14, junkslots 16, pockets 22, buttresses 24, internal longitudinal bore andfluid passageways (not shown), and other features of the drill bit 10.

The cutting elements 18 of an earth-boring rotary drill bit often have agenerally cylindrical shape. Therefore, to form a pocket 22 forreceiving such a cutting element 18 therein, it may be necessary ordesirable to form a recess into the body of a drill bit that having theshape of a flat-ended, right cylinder. Such a recess may be machinedinto the body of a drill bit by, for example, using a drilling ormilling machine to plunge a rotating flat-bottomed endmill cutter intothe body of a drill bit along the axis of rotation of the cutter. Such amachining operation may yield a cutting element pocket 22 having asubstantially cylindrical surface and a substantially planar end surfacefor disposing and brazing a generally cylindrical cutting element 18therein.

In some situations, however, difficulties may arise in machining suchgenerally cylindrical cutting element pockets 22. For instance, theremay be physical interference between the machining equipment used, suchas a multiple-axis milling machine, and the blades of the drill bitadjacent to the blade on which it is desired to machine a cuttingelement pocket 22. More specifically, the interference may inhibit adesired machining path of a machining tool that is aligned generallyalong the axis of rotation thereof because at least one of the machiningtool and the collet or chuck that retains the machining tool may contactan adjacent blade. As a result, in order to form the desired cuttingelement pocket 22 by way of a flat-bottomed machining tool, such as anendmill, the machining tool may be required to remove a portion of, forexample, a rotationally leading adjacent blade. As a furthercomplication, drill bits often have a radially central “cone” region onthe face thereof. In such a cone region, the profile of the face of thedrill bit tapers longitudinally away from the direction of drillingprecession as the profile approaches the center of the face of the drillbit. Thus, near the center of the bit, use of a flat-bottomed machiningtool to form recesses for generally cylindrical cutting elements may beextremely difficult.

As a result of such tool path interference problems, it maybe necessaryto orient one or more cutting element pockets 22 on the face of anearth-boring rotary drill bit at an angle that causes the cuttingelement 18 secured therein to exhibit a backrake angle that is greaterthan a desired backrake angle.

Methods for overcoming such tool path interference problems have beenpresented in the art. For example, U.S. Pat. No. 7,070,011 to Sherwood,Jr., et al. discloses steel body rotary drill bits having primarycutting elements that are disposed in cutter pocket recesses that arepartially defined by cutter support elements. The support elements areaffixed to the steel body during fabrication of the drill bits. At leasta portion of the body of each cutting element is secured to a surface ofthe steel bit body, and at least another portion of the body of eachcutting element matingly engages a surface of one of the supportelements.

However, there is a continuing need in the art for methods of formingcutting element pockets on earth-boring rotary drill bits that avoid thetool path interference problems discussed above and that do not requireuse of additional support elements.

BRIEF SUMMARY OF THE INVENTION

In some embodiments, the present invention includes methods of formingone or more cutting element pockets in a surface of an earth-boring toolsuch as, for example, a fixed cutter rotary drill bit, a roller conerotary drill bit, a core bit, an eccentric bit, a bicenter bit, areamer, or a mill. The methods include using a rotating cutter tomachine at least a portion of a cutting element pocket in such a way asto avoid mechanical tool interference problems and forming the pocket soas to sufficiently support a cutting element therein. For example,methods of the present invention may include machining at least aportion of a cutting element pocket using a rotating cutter oriented atan angle to a longitudinal axis of the cutting element pocket to beformed. In some embodiments, a first recess may be machined in a bitbody of an earth-boring tool to define a lateral sidewall surface of acutting element pocket using a rotating cutter oriented at an anglerelative to the longitudinal axis of the cutting element pocket beingformed. An additional recess may be machined in the bit body to defineat least a portion of an end surface of the cutting element pocket. Ascutting elements are often generally cylindrical in shape, the lateralsidewall surface and the end surface of the cutting element pocket maybe formed so as to enable a generally cylindrical cutting element tosimultaneously abut against each of the lateral sidewall surface and theend surface of the cutting element pocket.

In additional embodiments, the methods may include forming a firstsurface in a bit body that defines a lateral sidewall surface of acutting element pocket. At least a portion of the first surface may becaused to have a generally cylindrical shape centered about alongitudinal axis of the cutting element pocket. A substantially planarsecond surface may be formed that defines a back end surface of thecutting element pocket. Further, at least one additional surface may beformed that defines a groove located between the first surface and thesecond surface. The at least one additional surface may be caused toextend into the bit body in a generally radially outward direction fromthe longitudinal axis of the cutting element pocket radially beyond theat least a portion of the first surface.

In additional embodiments, the present invention includes methods offorming an earth-boring tool such as, for example, any of thosementioned above. The methods include forming a bit body and using arotating cutter to machine at least a portion of a cutting elementpocket in the bit body in a manner that avoids mechanical toolinterference problems and allows the pocket to be formed so as tosufficiently support a cutting element therein, as previously mentionedand described in further detail below.

In yet additional embodiments, the present invention includesearth-boring tools having a bit body comprising a first surface defininga lateral sidewall surface of a cutting element pocket, a second surfacedefining an end surface of the cutting element pocket, and at least oneadditional surface defining a groove located between the first andsecond surfaces that extends into the bit body in such a way as toenable a cutting element to abut against an area of each of the lateralsidewall surface and the end surface of the cutting element pocket. Insome embodiments, the cutting element pockets may be configured toreceive a generally cylindrical cutting element therein. For example, insome embodiments, at least a portion of the first surface that defines alateral sidewall surface of the cutting element pocket may be generallycylindrical in shape and may be centered about a longitudinal axis ofthe cutting element pocket. In such embodiments, the at least oneadditional surface may define a groove that extends into the bit body ina generally radially outward direction from the longitudinal axis of thecutting element pocket radially beyond the generally cylindrical portionof the first surface.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,various features and advantages of this invention may be more readilyascertained from the following description of the invention when read inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an earth-boring rotary drill bit;

FIG. 2A is a partial cross-sectional view of a bit body of anearth-boring rotary drill bit like that shown in FIG. 1 and illustratesa portion of a cutting element pocket being formed in the bit body inaccordance with one embodiment of the present invention; and

FIG. 2B is a partial cross-sectional view taken transversely through thepartially formed cutting element pocket shown in FIG. 2A along sectionline 2B-2B shown therein;

FIG. 3 is a partial cross-sectional view like that of FIG. 2Aillustrating a cutting element disposed within the partially formedcutting element pocket;

FIG. 4A is a partial cross-sectional view similar to that of FIG. 2A andillustrates another portion of the cutting element pocket being formedin the bit body shown therein;

FIG. 4B is a partial cross-sectional view taken transversely through thecutting element pocket shown in FIG. 4A along section line 4B-4B showntherein;

FIG. 5 is a partial cross-sectional view similar to that of FIG. 4Aillustrating a cutting element disposed within the cutting elementpocket and abutting against an area of both a lateral side wall and anend wall of the cutting element pocket;

FIG. 6 is a partial cross-sectional view of a bit body and illustrates aportion of a cutting element pocket being formed in a bit body inaccordance with another embodiment of the present invention;

FIG. 7 is a partial cross-sectional view of a bit body and illustrates aportion of a cutting element pocket being formed in a bit body inaccordance with yet another embodiment of the present invention;

FIG. 8 is a partial cross-sectional view like that of FIG. 7 andillustrates another portion of the cutting element pocket being formedin the bit body shown therein;

FIG. 9A is a partial longitudinal cross-sectional view like that of FIG.5 further illustrating filler material disposed within the cuttingelement pocket around the cutting element therein;

FIG. 9B is a partial cross-sectional view taken transversely through thestructure shown in FIG. 9A along section line 9B-9B shown therein andillustrates additional filler material disposed within the cuttingelement pocket over the cutting element therein;

FIG. 10 is another partial transverse cross-sectional view similar tothat of FIG. 9B illustrating filler material disposed substantiallyentirely over a portion of a cutting element within a cutting elementpocket;

FIG. 11 is a side view of an embodiment of a cutting element;

FIG. 12 is a side view of an embodiment of a cutting element of thepresent invention;

FIG. 13A is a plan view of a face of an embodiment of an earth-boringrotary drill bit of the present invention having a plurality of cuttingelement pockets similar to that shown in FIGS. 4A and 4B;

FIG. 13B is an enlarged perspective view of two primary cutting elementsof the drill bit shown in FIG. 13A each disposed within a cuttingelement pocket similar to that shown in FIGS. 4A and 4B; and

FIG. 13C is an enlarged perspective view of two backup cutting elementsof the drill bit shown in FIG. 13A each disposed within a cuttingelement pocket similar to that shown in FIGS. 4A and 4B.

DETAILED DESCRIPTION OF THE INVENTION

The illustrations presented herein are, in some instances, not actualviews of any particular cutting element insert, cutting element, ordrill bit, but are merely idealized representations which are employedto describe the present invention. Additionally, elements common betweenfigures may retain the same numerical designation.

In some embodiments, the present invention includes methods of formingcutting element pockets that avoid or overcome at least some of theinterference problems associated with previously known methods offorming such pockets, as well as the resulting cutting element pocketsthat are formed using such methods.

FIG. 2A is a partial cross-sectional view of a bit body 50 andillustrates a first recess 52 being formed in a formation-engagingsurface or face 54 of the bit body 50 to define at least one surface 55of the bit body 50 within a cutting element pocket. The recess 52 may beformed in the bit body 50 using a machining process. By way of exampleand not limitation, the recess 52 may be formed using a rotating cutter56 of a multi-axis milling machine (not shown). In some embodiments, thecutter 56 of the milling machine may comprise a so-called “endmill”cutter, and optionally, a so-called “ballnose” endmill cutter, which areoften used when milling three dimensional surfaces. As used herein, theterm “ballnose” endmill cutter means an endmill cutter having a curvedor rounded (e.g., hemispherical) cutting profile on the end thereof. Insome methods, the cutter 56 may have a radius that is significantlysmaller than the smallest radius of curvature of the surface 55 to beformed therewith.

In some embodiments, the cutting element that is desired to be securedto the face 54 of the bit body 50 in the cutting element pocket may havea generally cylindrical body comprising a generally cylindrical lateralsidewall surface extending between two substantially planar endsurfaces. Such configurations are commonly used for polycrystallinediamond compact (PDC) cutters. As a result, the cutting element pocketto be formed also may have a generally cylindrical shape that iscomplementary to the cutting element to be secured therein.

FIG. 2B is a cross-sectional view of the bit body 50 shown in FIG. 2Ataken through the recess 52 along section line 2B-2B shown therein. Ascan be seen with combined reference to FIGS. 2A and 2B, the surface 55of the bit body 50 within the recess 52 may comprise a lateral sidewallsurface of the cutting element pocket to be formed, and at least aportion 58 (FIG. 2B) of the lateral sidewall surface 55 may have agenerally cylindrical shape. The generally cylindrical portion 58 of thesurface 55 may be centered about a longitudinal axis 60 (FIG. 2A) of thecutting element pocket. The longitudinal axis 60 of the cutting elementpocket may be defined as an axis extending through the cutting elementpocket that would be coincident with the longitudinal axis of a cuttingelement properly secured within the cutting element pocket.

As shown in FIG. 2B, the surface 55 has a three-dimensional contour orshape and may be machined by moving the cutter 56 in the directionsindicated by the directional arrows shown in FIGS. 2A and 2B while thecutter 56 is oriented at a right angle (i.e., ninety degrees (90°)) oran acute angle (i.e., between zero degrees (0°)) and ninety degrees(90°)) relative to the longitudinal axis 60 (FIG. 2A). The angle betweenthe cutter 56 and the longitudinal axis 60 may be varied as necessary ordesired while machining the recess 52 in the bit body 50. As the surface55 of the bit body 50 may be machined using a cutter 56 oriented at aright angle (i.e., ninety degrees (90°))) or an acute angle (i.e.,between zero degrees (0°)) and ninety degrees (90°)) relative to thelongitudinal axis 60 (FIG. 2A) (as opposed to being aligned with thelongitudinal axis 60), the previously described mechanical interferenceproblems associated with machining a recess in a bit body to form acutting element pocket may be reduced or eliminated.

Referring again to FIG. 2A, as the surface 55 of the bit body 50 withinthe recess 52 is machined, a substantially planar front (rotationallyforward) end surface 64 and a substantially planar back (rotationallytrailing) end surface 66 of the bit body 50 also may be formed. A curvedor so-called “radiused” surface 68 may extend between the lateralsidewall surface 55 and each of the end surfaces 64, 66, as also shownin FIG. 2A.

FIG. 3 is a longitudinal cross-sectional view like that of FIG. 2A andillustrates a cutting element 18 disposed within the recess 52. As canbe appreciated with reference to FIG. 3, the curved or radiused surface68 disposed between the lateral sidewall surface 55 and thesubstantially planar back end surface 66 prevents the generallycylindrical cutting element 18 from simultaneously abutting against anysignificant area of both the lateral sidewall surface 55 and thesubstantially planar back end surface 66 of the bit body 50. It may bedesired to enable the cutting element 18 to simultaneously abut againstan area of each of the lateral sidewall surface 55 and the substantiallyplanar back end surface 66 to provide increased or maximum support andreinforcement to the cutting element 18 during drilling operations.

Referring to FIG. 4A, to enable the cutting element 18 to abut againstan area (as opposed to merely a point or along a line of contact) ofeach of the lateral sidewall surface 55 and the substantially planarback end surface 66 of the bit body 50 within the cutting elementpocket, an additional recess or groove 70 may be formed in the bit body50 at or near the intersection between the substantially planar back endsurface 66 and the lateral sidewall surface 55 within the recess 52 toremove the curved or radiused surface 68 therebetween and form anembodiment of a cutting element pocket 80 of the present invention. Thisprocess of removing or displacing the curved or radiused surface 68between the substantially planar back end surface 66 and the lateralsidewall surface 55 within the recess 52 may be referred to as“undercutting” an end of the recess 52, and the additional recess orgroove 70 may provide a so-called “undercut” or “relief” for a cuttingelement to be secured within the cutting element pocket 80.

FIG. 4B is a cross-sectional view of the bit body 50 shown in FIG. 4Ataken through the additional recess or groove 70 along section line4B-4B shown in FIG. 4A. As can be seen with combined reference to FIGS.4A and 4B, the additional recess or groove 70 may be defined by one ormore surfaces 72 of the bit body 50 that extend in a generally radiallyoutward direction from the longitudinal axis 60 (FIG. 4A) of the cuttingelement pocket 80 radially beyond at least the generally cylindricalportion 58 of the lateral sidewall surface 55. In some embodiments, atleast a portion of the additional recess or groove 70 may have agenerally annular shape and may extend about the longitudinal axis 60 ofthe cutting element pocket 80 at or near the intersection between thesubstantially planar back end surface 66 and the lateral sidewallsurface 55 within the recess 52.

The additional recess or groove 70 may be formed in the bit body 50using a machining process substantially similar to that previouslydescribed with reference to the recess 52 shown in FIGS. 2A and 2B, andmaybe machined using a rotating cutter 56 oriented at an angle (i.e., aright angle or an acute angle) relative to the longitudinal axis 60 ofthe cutting element pocket 80. In some embodiments, the additionalrecess or groove 70 may be formed in the bit body 50 using the samerotating cutter 56 used to form the recess 52, and the groove 70 maybeformed during the same machining process or sequence as the recess 52.For example, in some embodiments, the recess 52 and the groove 70 may beformed sequentially in a single machining process or sequence carriedout by a milling machine. As another example, in some embodiments, therecess 52 and the groove 70 may be formed together generallysimultaneously in a single machining process or sequence carried out bya milling machine. In yet other embodiments, the recess 52 and thegroove 70 may be formed sequentially in different machining processes orsequences.

Referring to FIG. 5, by forming the additional recess or groove 70 toundercut the recess 52, the substantially planar back end surface 66 ofthe cutting element pocket 80 maybe sized and configured to allow alateral sidewall surface 26 and a substantially planar back end surface28 of a cutting element 18 to simultaneously abut against each of thelateral sidewall surface 55 and the substantially planar back endsurface 66 of the bit body 50, respectively, within the cutting elementpocket 80. In other words, the contact areas of the substantially planarback end surface 66 of the cutting element pocket 80 may be increased byforming the additional recess or groove 70 to undercut the recess 52such that the area of the back end surface 66 encompassed by a boundarydefined by the projection of at least the portion 58 of the lateralsidewall surface 55 onto the back end surface 66 is substantiallyplanar. In this configuration, a cutting element 50 can simultaneouslyabut against each of the lateral sidewall surface 55 and thesubstantially planar back end surface 66 within the cutting elementpocket 80, as shown in FIG. 5.

As previously mentioned, the additional recess or groove 70 maybemachined in the bit body 50 using a rotating cutter 56 oriented at aright angle relative to the longitudinal axis 60 of the cutting elementpocket 80, as shown in FIG. 4A. In additional embodiments of the presentinvention, the additional recess or groove 70 may be machined in the bitbody 50 using a rotating cutter 56 oriented at an acute angle of lessthan ninety degrees (90°) relative to the longitudinal axis 60 of thecutting element pocket 80, as shown in FIG. 6. As a non-limitingexample, the cutter 56 may be oriented at an acute angle of betweenabout ninety degrees (90°)) and about thirty degrees (30°)) relative tothe longitudinal axis 60 of the cutting element pocket 80 when formingthe additional recess or groove 70. In some such methods, both thelateral sidewall surface 55 and the substantially planar back endsurface 66 within the cutting element pocket 80 may be undercut by theadditional recess or groove 70, as also shown in FIG. 6.

As previously described, in some embodiments of the present invention,the recess 52 maybe formed prior to the recess or groove 70, and therecess or groove 70 maybe formed in or cause to intersect one or moresurfaces of the bit body 50 that are exposed within the recess 52. Inadditional embodiments, the recess or groove 70 may be formed prior toforming the recess 52, and the recess 52 may be formed in or caused tointersect one or more surface of the bit body 50 that are exposed withinthe recess or groove 70.

Referring to FIG. 7, for example, a recess or groove 70′ may be formedin the bit body 50 to form a substantially planar surface 66 of the bitbody. In some embodiments, for example, the recess or groove 70′ may begenerally planar or disc-shaped, and may be oriented substantiallytransverse to the longitudinal axis 60. Such a generally planar recessor groove 70′ may be partially defined by the substantially planarsurface 66 of the bit body 50 exposed within the recess or groove 70′, asecond, opposing substantially planar surface 67 of the bit body 50exposed within the recess or groove 70′, and one or more surfaces 72that extend between the first and second planar surfaces 66, 67 of thebit body 50 and are exposed within the recess or groove 70′. The recessor groove 70′ may be machined in the bit body 50 in a mannersubstantially similar to that previously described in relation to thegroove 70 and FIGS. 4A and 4B.

As shown in FIG.8, a recess 52′ then maybe formed in the bit body 50 todefine the lateral side wall surface 55 of the cutting element pocket80. The recess 52′ may be caused to intersect the second substantiallyplanar surface 67′ (FIG. 7) of the bit body 50 exposed within the recessor groove 70′. The recess 52′ may be machined in the bit body 50 in amanner substantially similar to that previously described in relation tothe recess 52 and FIGS. 2A and 2B.

After forming the recess or groove 70′ and the recess 52′, the firstsubstantially planar surface 66 may define a substantially planar backend surface of the cutting element pocket 80, and the lateral side wallsurface 55 may define a lateral side wall surface of the cutting elementpocket 80.

Although the cutting element pocket 80 illustrated in FIGS. 4A, 4B, and5 is configured to receive a generally cylindrical cutting element 18therein, in additional embodiments, the cutting element pocket 80,including the recess 52 and the additional recess or groove 70, may beconfigured to receive cutting elements 18 having other shapes andconfigurations.

The present invention has utility in relation to earth-boring rotarydrill bits having bit bodies substantially comprised of a metal or metalalloy such as steel. Recently, new methods of forming rotary drill bitshaving bit bodies comprising particle-matrix composite materials havebeen developed in an effort to improve the performance and durability ofearth-boring rotary drill bits. Such methods are disclosed in pendingU.S. patent application Ser. No. 11/271,153, filed Nov. 10, 2005 andpending U.S. patent application Ser. No. 11/272,439, also filed Nov. 10,2005, the disclosure of each of which application is incorporated hereinin its entirety by this reference.

In contrast to conventional infiltration methods (in which hardparticles (e.g., tungsten carbide) are infiltrated by a molten liquidmetal matrix material (e.g., a copper based alloy) within a refractorymold), these new methods generally involve pressing a powder mixture toform a green powder compact, and sintering the green powder compact toform a bit body. The green powder compact may be machined as necessaryor desired prior to sintering using conventional machining techniqueslike those used to form steel bit bodies. Furthermore, additionalmachining processes may be performed after sintering the green powdercompact to a partially sintered brown state, or after sintering thegreen powder compact to a desired final density. For example, it may bedesired to machine cutting element pockets on one or more blades 14(FIG. 1) of a bit body formed by such a process while the bit body is inthe green, brown, or fully sintered state. However, as with steel-bodieddrill bits, interference problems may prevent the formation of thedesired cutting element pockets. To overcome such interference problems,methods of the present invention, such as those previously describedherein, may be used to form one or more cutting element pockets 80 inone or more blades (such as the blades 14 shown in FIG. 1) of a bit body50 formed by such a process while the bit body 50 is in the green,brown, or fully sintered state. Therefore, the present invention alsohas utility in relation to earth-boring tools having bit bodiessubstantially comprised of a particle-matrix composite material.

After forming one or more cutting element pockets 80 in a bit body 50 ofan earth-boring rotary drill bit as previously described, a cuttingelement 18 may be positioned within each cutting element pocket 80 andsecured to the bit body 50. By way of example and not limitation, eachcutting element 18 may be secured within a cutting element pocket 80using a brazing alloy, a soldering alloy, or an adhesive material.

As shown in FIG. 5, after securing each cutting element 18 within acutting element pocket 80, one or more spaces or voids may be disposedwithin the cutting element pocket 80 around at least a portion of thecutting element 18. For example, the recess or groove 70 may comprise ordefine a space or void around the cutting element 18 within the cuttingelement pocket 80. Additionally, the portion of the recess 52 located infront of (rotationally forward relative to) the cutting element 18 maycomprise or define another space or void around the cutting element 18within the cutting element pocket 80. Such spaces or voids mayfacilitate wear of the surrounding elements or portions of the drill bitduring a drilling operation, which could potentially result inseparation of the cutting element 18 from the bit body 50 whiledrilling. The spaces or voids within the cutting element pocket 80around the cutting element 18 may be filled with a filler material, asdiscussed in further detail below, to prevent wear during drillingoperations.

Referring to FIG. 9A, the spaces or voids defined by the recess orgroove 70 and the portion of the recess 52 located in front of thecutting element 18 may be filled with a filler material 84. FIG. 9B is apartial transverse cross-sectional view of the structure shown in FIG.9A taken along section line 9B-9B shown therein. As shown in FIG. 9B,additional filler material 84 also may be disposed within the cuttingelement pocket 80 over at least a portion of the cutting element 18 toreduce or eliminate any recesses or voids extending into the cuttingelement pocket 80 below the face 54 of the bit body 50.

FIG. 10 is a partial transverse cross-sectional view taken through acutting element pocket 80 and cutting element 18 positioned therein,similar to that of FIG. 9B. As shown in FIG. 10, in some situations, atleast a portion of the cutting element 18 may be substantially entirelyrecessed within the cutting element pocket 80 below the face 54 of thebit body 50. In such cases, filler material 84 may be provided entirelyover at least a portion of the cutting element 18 within the cuttingelement pocket 80.

By way of example and not limitation, the filler material 84 shown inFIGS. 9A, 9B, and 10 may comprise a welding alloy, a solder alloy, or abrazing alloy, and may be applied using a corresponding welding,soldering, or brazing process.

In additional embodiments, the filler material 84 may comprise ahardfacing material (e.g., a particle-matrix composite material) and maybe applied using a welding process (e.g., arc welding processes, gaswelding processes, resistance welding processes, etc.) or a flamesprayprocess. By way of example and not limitation, any of the hardfacingmaterials described in pending U.S. patent application Ser. No.11/513,677, filed Aug. 30, 2006, the disclosure of which is incorporatedherein in its entirety by this reference, may be used as the fillermaterial 84, and may be applied to the bit body 50 as described therein.Furthermore, in some embodiments, the filler material 84 may comprise atleast one of a welding alloy, a solder alloy, or a brazing alloy, andhardfacing material may be applied over the exposed surfaces thereof tominimize or prevent wear during drilling operations. Such layeredcombinations of materials may be selected to form a composite or gradedstructure between the cutting element 18 and the surrounding bit body 50that is selected to tailor at least one of the strength, toughness, wearperformance, and erosion performance of the region immediatelysurrounding the cutting element 18 for the particular design of thedrilling tool, location of the cutting element 18 on the drilling tool,or the application in which the drilling tool is to be used.

In yet other embodiments, at least a portion of the filler material 84may be or comprise a preformed solid structure that is constructed andformed to have a shape corresponding to that of at least a portion of arecess or void within the cutting element pocket 80 around the cuttingelement 18. As a non-limiting example, the filler material 84 shown inFIG. 10 over the cutting element 18 may comprise a preformed solid capstructure that may be positioned over the cutting element 18 within thecutting element pocket 80 and secured to the bit body 50.

Such a preformed solid structure maybe separately fabricated, positionedat a location within the cutting element pocket 80 selected to fill aspace or void, and secured to one or more surrounding surfaces of thebit body 50. The preformed solid structure maybe secured to one or moresurrounding surfaces of the bit body 50 using, for example, an adhesive,a brazing process, a flamespray process, or a welding process. In someembodiments, a preformed solid structure may be positioned within thecutting element pocket 80 and secured to the bit body 50 after securinga cutting element 18 in the cutting element pocket 80. In additionalembodiments, such a preformed solid structure may be positioned withinthe cutting element pocket 80 and secured to the bit body 50 prior tosecuring a cutting element 18 in the cutting element pocket 80. In yetother embodiments, one or more such preformed solid structures maybesecured to a cutting element 18 prior to securing the cutting element 18within the cutting element pocket 80.

In some embodiments, such a preformed solid structure may comprise arelatively abrasive and wear-resistant material such as aparticle-matrix composite material comprising a plurality of hardparticles (e.g., tungsten carbide) dispersed throughout a metal or metalalloy matrix material (e.g., a nickel or cobalt based metal alloy), soas to further prevent wear of the material surrounding the cuttingelement 18 during drilling operations.

FIG. 11 is a side view of a cutting element 18. As shown in FIG. 11, insome embodiments, the cutting element 18 may comprise a diamond table 85formed on or otherwise secured to a surface of a first substrate 86. Anopposing surface of the first substrate 86 may be secured to a surfaceof a second, relatively larger substrate 87. The first substrate 86 may,in some embodiments, have a disc shape, and the relatively largersubstrate 87 may have an elongated shape. For example, it may be desiredto have a substrate having a shape similar to the composite shape formedby the first substrate 86 and the second substrate 87. It may bedifficult, however, to form a diamond table 85 on a surface of such asubstrate. As a result, it maybe necessary or desired to form a diamondtable on a relatively smaller substrate, such as the first substrate 86,and then secure the relatively smaller substrate to a relatively largersubstrate, such as the second substrate 87 to provide a compositesubstrate having the desired shape.

FIG. 12 illustrates an embodiment of a cutting element 18A of thepresent invention. As shown in FIG. 12, the cutting element 18Acomprises a relatively smaller first substrate 86A and a relativelylarger substrate 87A. The cutting element 18A may have one or morefeatures 88 integrally formed therewith that are sized, shaped, andotherwise configured to fill at least a portion of a recess or voidwithin the cutting element pocket 80 around the cutting element 18. Forexample, one or more such features 88 may be integrally formed with atleast one of the first substrate 86A and the second substrate 87A. Byway of example and not limitation, cutting element 18A may have afeature 88 integrally formed with the second substrate 87A that has asize and shape configured to fill a recess 70 (such as that previouslydescribed with reference to FIG. 4A-4B), as shown in FIG. 12. Inadditional embodiments, the cutting element 18A may comprise one or moreadditional features 88 sized and configured to fill at least a portionof a recess or void located over the cutting element 18A within thecutting element pocket 80, such as those previously described withreference to FIGS. 9B and 10.

FIG. 13A is a plan view of the face of an embodiment of an earth-boringrotary drill bit 90 of the present invention. The earth-boring rotarydrill bit 90 includes a bit body 92 having a plurality of generallyradially-projecting and longitudinally-extending wings or blades 94,which are separated by junk slots 96 extending from channels on the faceof the bit body 92. A plurality of primary PDC cutting elements 18 areprovided on each of the blades 94 within cutting element pockets 80(FIGS. 4A-4B). A plurality of secondary PDC cutting elements 18′ arealso provided within cutting element pockets 80 on each of the blades 94rotationally behind the primary cutting elements 18.

FIG. 13B is an enlarged perspective view illustrating two primarycutting elements 18 that have been secured within cutting elementpockets 80 formed using methods of the present invention, as previouslydescribed herein. Similarly, FIG. 13C is an enlarged perspective viewillustrating two secondary cutting elements 18′ that have also beensecured within cutting element pockets 80 formed using methods of thepresent invention, as previously described herein.

While the present invention has been described herein in relation toembodiments of earth-boring rotary drill bits that include fixedcutters, other types of earth-boring tools such as, for example, corebits, eccentric bits, bicenter bits, reamers, mills, roller cone bits,and other such structures known in the art may embody teachings of thepresent invention and may be formed by methods that embody teachings ofthe present invention, and, as used herein, the term “bit body”encompasses bodies of earth-boring rotary drill bits, as well as bodiesof other earth-boring tools including, but not limited to, core bits,eccentric bits, bicenter bits, reamers, mills, roller cone bits, as wellas other drilling and downhole tools.

By using embodiments of cutting element pockets 80 of the presentinvention, cutters (primary cutters and backup cutters) may be securedto the face of a bit body at practically any location thereon, and thecutting element pockets 80 may be configured to provide any selectedbackrake angle to a cutting element secured therein, withoutencountering mechanical tool interference problems. As a result,earth-boring drilling tools, such as the earth-boring rotary drill bit90 shown in FIG. 13A may be provided that are capable of drilling atincreased rates of penetration relative to previously known drillingtools having machined cutter pockets, and similar to rates ofpenetration achieved using drilling tools having cutter pockets formedin a casting process (e.g., infiltration).

Furthermore, while the present invention has been described herein withrespect to certain preferred embodiments, those of ordinary skill in theart will recognize and appreciate that it is not so limited. Rather,many additions, deletions and modifications to the preferred embodimentsmay be made without departing from the scope of the invention ashereinafter claimed. In addition, features from one embodiment may becombined with features of another embodiment while still beingencompassed within the scope of the invention as contemplated by theinventors. Further, the invention has utility with different and variousbit profiles as well as cutter types and configurations.

1. A method of forming a cutting element pocket in an earth-boring tool,the method comprising: machining a first recess in an earth-boring tooland defining a lateral sidewall surface of a cutting element pocketusing a rotating cutter oriented at an angle relative to a longitudinalaxis of the cutting element pocket; machining a second recess in theearth-boring tool and defining at least a portion of an end surface ofthe cutting element pocket; and forming the lateral sidewall surface andthe end surface of the cutting element pocket to enable a generallycylindrical cutting element to simultaneously abut against an area ofeach of the lateral sidewall surface and the end surface of the cuttingelement pocket.
 2. The method of claim 1, wherein using a rotatingcutter comprises using an endmill cutter.
 3. The method of claim 2,wherein using an endmill cutter comprises using a ballnose endmillcutter.
 4. The method of claim 1, wherein machining a second recessfurther comprises machining the second recess after machining the firstrecess.
 5. The method of claim 1, wherein machining a second recessfurther comprises machining the second recess prior to machining thefirst recess.
 6. The method of claim 1, wherein machining a secondrecess further comprises using the same rotating cutter used to machinethe first recess to machine the second recess.
 7. The method of claim 6,wherein using the same rotating cutter used to machine the first recessto machine the second recess further comprises orienting the rotatingcutter at an angle relative to the longitudinal axis of the cuttingelement pocket while machining the second recess.
 8. The method of claim1, wherein machining a second recess in the drill bit comprisesmachining a groove in a surface of the drill bit exposed within thefirst recess.
 9. The method of claim 8, wherein machining a groovecomprises machining a groove, at least a portion of the groove having agenerally annular shape.
 10. The method of claim 1, wherein machining asecond recess in the drill bit comprises machining a generally planarrecess in the drill bit oriented substantially transverse to thelongitudinal axis of the cutting element pocket.
 11. The method of claim10, wherein machining the first recess further comprises causing thefirst recess to intersect the generally planar recess.
 12. The method ofclaim 1, wherein forming the lateral sidewall surface and the endsurface of the cutting element pocket to enable a generally cylindricalcutting element to simultaneously abut against each of the lateralsidewall surface and the end surface of the cutting element pocketcomprises causing at least a portion of the second recess to extend in agenerally radially outward direction from the longitudinal axis of thecutting element pocket beyond at least a portion of the lateral sidewallsurface of the cutting element pocket.
 13. A method of forming anearth-boring tool, the method comprising: forming a bit body; andforming at least one cutting element pocket in the bit body, comprising:machining a first recess in a surface of the bit body and defining alateral sidewall surface of a cutting element pocket using a rotatingcutter oriented at an angle relative to a longitudinal axis of thecutting element pocket; machining a second recess in the bit body anddefining at least a portion of an end surface of the cutting elementpocket; and forming the lateral sidewall surface and the end surface ofthe cutting element pocket to enable a generally cylindrical cuttingelement to simultaneously abut against an area of each of the lateralsidewall surface and the end surface of the cutting element pocket. 14.The method of claim 13, wherein forming a bit body comprises: providinga powder mixture; and pressing the powder mixture to form a green bitbody.
 15. The method of claim 14, wherein at least one of machining afirst recess and machining a second recess comprises machining the greenbit body.
 16. The method of claim 14, wherein forming a bit body furthercomprises partially sintering the green bit body to form a brown bitbody.
 17. The method of claim 16, wherein at least one of machining afirst recess and machining a second recess comprises machining the brownbit body.
 18. The method of claim 17, wherein forming a bit body furthercomprising sintering the brown bit body to a desired final density. 19.The method of claim 14, wherein forming a bit body further comprisessintering the green bit body to a desired final density.
 20. The methodof claim 19, wherein at least one of machining a first recess andmachining a second recess comprises machining the bit body aftersintering the green bit body to a desired final density.
 21. The methodof claim 14, wherein forming a bit body comprises forming a bit bodycomprising a particle-matrix composite material.
 22. The method of claim13, wherein forming a bit body comprises forming a bit bodypredominantly comprised of a metal or metal alloy.
 23. The method ofclaim 22, wherein forming a bit body comprises forming a steel bit body.24. The method of claim 13, wherein using a rotating cutter comprisesusing an endmill cutter.
 25. The method of claim 24, wherein using anendmill cutter comprises using a ballnose endmill cutter.
 26. The methodof claim 13, wherein machining a second recess further comprisesmachining the second recess after machining the first recess.
 27. Themethod of claim 13, wherein machining a second recess further comprisesmachining the second recess prior to machining the first recess.
 28. Themethod of claim 13, wherein machining a second recess further comprisesusing the same rotating cutter used to machine the first recess tomachine the second recess.
 29. The method of claim 28, wherein using thesame rotating cutter used to machine the first recess to machine thesecond recess further comprises orienting the rotating cutter at anangle relative to the longitudinal axis of the cutting element pocketwhile machining the second recess.
 30. The method of claim 13, whereinmachining a second recess in the bit body comprises machining a groovein a surface of the bit body exposed within the first recess.
 31. Themethod of claim 30, wherein machining a groove comprises machining agroove, at least a portion of the groove having a generally annularshape.
 32. The method of claim 13, wherein machining a second recess inthe bit body comprises machining a generally planar recess in the bitbody oriented substantially transverse to the longitudinal axis of thecutting element pocket.
 33. The method of claim 32, wherein machiningthe first recess further comprises causing the first recess to intersectthe generally planar recess.
 34. The method of claim 13, furthercomprising: securing a cutting element within the at least one cuttingelement pocket; and filling at least a portion of a void within at leastone of the first recess and the second recess around the cutting elementwith a filler material.
 35. The method of claim 34, wherein filling atleast a portion of a void within at least one of the first recess andthe second recess around the cutting element with a filler materialcomprises filling the at least a portion of the void with at least oneof a brazing alloy, a soldering alloy, a welding alloy, and a hardfacingmaterial.
 36. The method of claim 34, wherein filling at least a portionof a void within at least one of the first recess and the second recessaround the cutting element with a filler material comprises filling theat least a portion of the void with a preformed solid structure.
 37. Themethod of claim 36, wherein filling the at least a portion of the voidwith a preformed solid structure comprises at least one of brazing,welding, and flamespraying the preformed solid structure to the bitbody.
 38. The method of claim 36, wherein filling the at least a portionof the void with a preformed solid structure further comprises formingthe preformed solid structure to comprise a particle-matrix compositematerial.
 39. An earth-boring tool having a bit body comprising: a firstsurface defining a lateral sidewall surface of a cutting element pocket,at least a portion of the first surface having a generally cylindricalshape centered about a longitudinal axis of the cutting element pocket;a substantially planar second surface defining a back end surface of thecutting element pocket; and at least one additional surface defining agroove located between the first surface and the second surface andextending into the bit body in a generally radially outward directionfrom the longitudinal axis of the cutting element pocket beyond the atleast a portion of the first surface.
 40. The earth-boring tool of claim39, wherein the bit body is predominantly comprised of steel.
 41. Theearth-boring tool of claim 39, wherein the bit body is predominantlycomprised of a particle-matrix composite material.
 42. The earth-boringtool of claim 39, further comprising a cutting element secured withinthe at least one cutting element pocket.
 43. The earth-boring tool ofclaim 42, further comprising a filler material disposed within at leasta portion of the at least one cutting element pocket around the cuttingelement.
 44. The earth-boring tool of claim 43, wherein the fillermaterial comprises at least one of a brazing alloy, a soldering alloy, awelding alloy, and a hardfacing material.
 45. The earth-boring tool ofclaim 43, wherein the filler material comprises a preformed solidstructure.
 46. The earth-boring tool of claim 45, wherein the preformedsolid structure is at least one of brazed, welded, and flamesprayed tothe bit body.
 47. The earth-boring tool of claim 45, wherein thepreformed solid structure comprises a particle-matrix compositematerial.
 48. A method of forming an earth-boring tool, the methodcomprising: forming a bit body; and forming at least one cutting elementpocket in the bit body, comprising: forming a first surface in the bitbody defining a lateral sidewall surface of the at least one cuttingelement pocket and causing at least a portion of the first surface tohave a generally cylindrical shape centered about a longitudinal axis ofthe cutting element pocket; forming a substantially planar secondsurface defining a back end surface of the cutting element pocket; andforming at least one additional surface defining a groove locatedbetween the first surface and the second surface and causing the atleast one additional surface to extend into the bit body in a generallyradially outward direction from the longitudinal axis of the cuttingelement pocket beyond the at least a portion of the first surface. 49.The method of claim 48, wherein at least one of forming a first surface,forming a substantially planar second surface, and forming at least oneadditional surface comprises machining a recess in the bit body using arotating cutter oriented at an angle relative to the longitudinal axisof the at least one cutting element pocket.
 50. The method of claim 49,wherein forming a first surface comprises machining a recess in the bitbody using the rotating cutter oriented at an angle relative to thelongitudinal axis of the at least one cutting element pocket.
 51. Themethod of claim 49, wherein using a rotating cutter comprises using anendmill cutter.
 52. The method of claim 51, wherein using an endmillcutter comprises using a ballnose endmill cutter.
 53. The method ofclaim 48, wherein forming a substantially planar second surface furthercomprises forming the substantially planar second surface after formingthe first surface in the bit body.